Wrench operated tap changer mechanism



p 1951 F. E. GROMMES 2,568,887

WRENCH OPERATED TAP CHANGER MECHANISM Filed June 28, 1949 mung,

Patented Sept. 25, l951 WRENCH OPERATED TAP CHANGER MECHANISM Frank E. Grommes, Pittsburgh, Pa., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application June 28, 1949, Serial No. 101,877

This invention relates to electric switch apparatus and cooperating switch operating mechanism and in particular relates to means for moving the switch apparatus from one predetermined position to another predetermined position with a snap action and for preventing separation of part of the switch operating mechanism from the switch apparatus when the switch apparatus is not in a predetermined position.

The invention is particularly suitable for use with electric induction apparatus having tap changing equipment associated with the induction apparatus and located inside an enclosing casing. The tap changer for such apparatus, being located within the enclosing casing and being manually operated, is operated by an per-.

ator with a wrench from outside of the casing. The cover of the casing may have an- Opening therein with a cap which can be removed when it is desirable to change taps, and a wrench can then be inserted through the opening to operate the switch apparatus of the tap changer.

The use of tap changer equipment in this man.

ner with electric induction apparatus is disclosed in the prior art. However, such previously disclosed mechanism does not provide a snap operation of the switch apparatus when a tap change is made from one predetermined position to another predetermined position nor does it interlock the operating element or wrench with the switch apparatus as a change of the taps from one position to the next is being accomplished.

In the prior art it has been suggested to have a detent associated with the tap changer mechanism for causing a snap action as the tap changer is moved to each predetermined position. In other prior art disclosures switch apparatus is provided with protective equipment to insure that the operating wrench cannot be removed from the casing enclosing the switch apparatus unless the wrench is aligned in a particular manner with respect to the opening in the casing; in particular, the opening through which the wrench is inserted is provided with notches with which lugs on the operating wrench must align before the wrench can be removed from the casing. However, the type of apparatus disclosed in the prior art is not entirely satisfactory for it does not provide a positive interlock between the operating element or wrench and the switching apparatus.

According to a preferred embodiment of this invention a transformer tap changing mechanism is operated with a wrench from outside the casing. A detent interlocks the wrench with 11 Claims. (Cl. 74548) 2 an operating shaft of the tap changing mechanism and prevents separation of the wrench from engagement with the operating shaft when the operating shaft has not been turned to a predetermined position.

Having in mind the defects of the prior art, the object of this invention is to provide an improved switching apparatus.

Another object of this invention is to provide a wrench operated switching apparatus which prevents separation of the operating wrench from the switching mechanism when the switch appa-v ratus is not in preselected positions.

Still another object is to provide an improved tap changer having a means for interlocking an operating wrench with an operating shaft of the tap changer when the taps are not in a preselected position.

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawings, in which:

Fig. 1 is an elevation view of the upper portion of a transformer showing a preferred embodiment of this invention adapted to the tap changin mechanism of the transformer;

Fig. 2 is an enlarged view in section of the tap changing mechanism taken along line II--II of Fig. 1, the mechanism being assumed to be brought to a tap position;

Fig. 3 is a sectional view taken along line IIIIII of Fig. 2;

Fig. 4 is a sectional view similar to Fig. 2 showing the tap changing mechanism in a position intermediate the two tap positions;

Fig. 5 is a sectional view of the tap changing mechanism taken along line VV of Fig. 4;

Fig. 6 is a view similar to Fig. 2 through a modified embodiment of the invention;

Fig. 7 is a View similar to Fig. 4 of the modification illustrated in Fig. 6; and

Fig. 8 is an enlarged view in elevation of the wrench used for changing the taps.

A tap changer II is shown in Fig. 1 associated with a three phase transformer 12 enclosed in a casing 13. The upper end frame 14 clamps the laminated steel core of the transformer I2 and also may be the supporting structure for the tap changer II and frame l6. Three tap changer insulation panels I! with fixed contact blocks I8 are vertically positioned above the upper end frame I4. Movable assemblies I9, 20, 2|, each having double contact shoes 22, 23, 24 are used to change taps by movement of the movable assemblies from one contact block to another. The

three movable assemblies i9, 20, 2| are controlled by a single control operating shaft 26. Movement of the operating shaft 26 is transmitted through bevel gears 21 to shaft 28 to which the movable contacts are attached. Thus all three phases of the transformer are tap changed together, eliminating any chance of one phase being connected differently from another.

The operating shaft 26 is turned by a special wrench 29 which is inserted through a hole 30 in the cover 3| of the transformer casing. When the wrench is not being used to change the taps, it is removed from the hole, and the hole is then sealed tightly by a pipe plug (not shown).

The wrench used for changing taps cannot be separated from engagement with the end of the operating shaft unless the tap changer has made a complete change from one tap position to the next tap position.

In the preferred embodiment this invention provides an interlock of the wrench '29 to the end 33 of the operating shaft 26. An operating nut 34 is formed integrally with the end 33 of the operating shaft or is fixed thereto in any suitable known manner as by a tapered pin 35. Since the base portion of the operating nut is fixed to the operating shaft 26, they can be rotated together about the longitudinal axis of the operating shaft. The upper portion of the operating nut may have any polygonal shape, preferably the hexagonal shape, as shown, or it may have a splined upper portion. The nut thus defines driving surfaces by which 'the sock et 35 of the wrench '29 can cooperate to turn the operating nut and shaft. The central portion of the operating nut has a hole 38 bored therein which serves as a pin retainer and .guide means. The hole 38 is located transversely to the axis of the operating shaft and the bore from one end is larger than the bore from the other end of the hole. The difference in diameters of the bores defines a shoulder 39 at the base of the larger bore.

A spring 4| is inserted into the large bore of the hole. A pin 42 having one end portion of greater diameter than the other end portion thereof is then inserted in the bore of the operating nut. The dimensions of the bore and the pin are such that the pin has a sliding fit in the bore of the operating nut. The smaller diamr,

eter portion of the pin is inserted into the larger bore of the hole, inside and through the convolutions of the spring, and into the smaller bore of the hole until shoulder 45 of the pin rests against the springp The pin is sufficiently long so that the larger end portion having a rounded end always protrudes from the hole of the operating nut, and at least part of the smaller end portion of the pin will protrude from the hole when'the shoulder 45 of the pin 42 is pushed against the spring 4|. I

The socket portion 36 of the wrench 29 has a hole 46 in the wall thereof which will ac commodate the small end portion of the pin, and diametrically opposite the hole 46 an opening is cut into the wall of the socket forming a notch or recess 41. The width of the recess is sufficient to accommodate the larger end portion of the pin without causing the wall of the socket to bind the pin as the wrench turns the operating nut. A tap position indicator 49 is shown fixed to the upper portion of the wrench outside the casing.

When the large portion of the pin 42 is in the recess 41 of the socket '35, the small bore in 4 the nut 34 is aligned with the hole 46 in the socket 36. If the rounded end of the pin is then pushed, the spring 4| will be compressed and the smaller end of the pin will extend into the hole 46 in the wall of the socket. The wrench will thereby be interlocked with the operating shaft. As soon as the force is relieved which caused the pin to move, the spring will force the pin out again, and the wrench can be separated from the shaft.

.A fixed annular collar 5| is coaxially spaced from the operating shaft and from the operating nut. The operating shaft, pin and wrench can rotate as a unit inside the annular collar.

The rounded end of the larger portion of the pin 42 bears against the inside or inner periphery 52 of the collar 5|. The collar has a portion formed of circumferentially spaced segments 53 radially tapered to form a cam surface on the side against which the rounded end of the pin bears. The adjacent ends of adjacent segments are spaced from each other a distance less than the diameter of the large end of the pin 42, .but the distance between the points 55 where the tapered portion begins on adjacent segments is greater than the diameter of the large end of the pin. Therefore as the rounded end of the pin 42 passes point 55 where the taper of any segment begins, the pin will extend a greater distance from theaxis of the 'nut. The taper of the ends of'thesegments will tend to cause the pin to move with snap action to a position where the rounded end of the pin '42 rests on the adjacent tapered ends of two adjacent segments. In this position the sma'll end of the pin will be retracted into the hole in the nut, and the wrench is not interlocked with the operating shaft. When the rounded end of the pin '42 is at less than its greatest distance from the axis of the nut, the small end of the pin extends from the hole in the nut into the hole in the socket and locks the wrench with the operating shaft.

Figs. 2 and 3 show the position of the preferred embodiment of the invention with the switch in a predetermined tap position. Figs. 4 and '5 show the switch apparatus in a given position intermediate tap positions. Tap positions are represented by the letters A to E and correspond to a'position of the large end of the pin abutting two adjacent segments of the collar. The taper of the segments is such that as the operating shaft, nut and pin is rotated, the large end of the pin will snap into a proper tap position and will center on the adjacent ends of two segments with a snap action.

Figs. 6 and '7 illustrate a modification of the invention in which the collar segments 51 are not tapered but are cut radially so that adjacent ends of adjacent segments are substantially parallel to each other and are spaced from each other a distance slightly greater than the diameter of the "large end 58 of the pin 59. The small end 6| of the pin has a hole 62 extending therethrough in a dlrection'normal to the longitudinal axis of the pin. A-dowel 63 having length greater than the length of the hole is inserted into the hole 62 in the pin 59.

A slot 64 is formed in the nut 65 and extends from the edge 66 thereof in a direction normal to the axis of the nut and shaft. The slot is wide enough to allow the dowel to move with the pin without binding in the slot. The depth of the slot is great enough to permit sufficient movement of the pin so that the small end El of the pin can extend from and retract into the nut: The end portions of the dowel 63 which extend from the hole 62 in the small end 6| of the pin stop the retraction of'the pin into the nut by abutting against the base 69 of the slot.

In the modification of the invention illustrated in Figs. 6 and 7, the large end of the pin is against the inner side or inner periphery of the segments at any position intermediate a tap position and the wrench is interlocked with the shaft as shown in Fig. '7. When the pin is rotated until the tip of the pin passes the end of a segment, the pin will snap into the space between the ends of adjacent segments as shown in Fig. 6. The dowel will limit the movement of pin to prevent the rounded end thereof from extending so far from the hole that the switching apparatus cannot be moved from one tap position to the next without difficulty.

Although but two embodiments of the present invention have been illustrated and described, it is apparent to one skilled in the art that various changes and modifications, including particularly those obtained by reversal of parts, may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a switch operating mechanism, the combination of an operating shaft, a wrench having a socket portion cooperative with said shaft for rotating said shaft, and means interlocking said shaft and said wrench, said means including an opening in said wrench, a spring biased pin retained within said shaft, and a fixed collar having a cam surface-one end of said pin bearing against said cam surfac'e'of said collar, whereby movement of said pin with respect to said cam surface in response to movement of said shaft into a given position causes said pin to penetrate said opening in said wrench to interlock said wrench and said shaft.

2. In a tap changer mechanism, the combination of an operating shaft, a wrench defining a socket cooperative with one end of said shaft for rotating said shaft, and means for interlocking said wrench and said shaft, said means comprising a hole in the wall of said socket and a detent cooperating with said end of saidshaft and said socket, said detent including an element movable transversely of the axis of said shaft and rotatable with said shaft and a fixed collar coaxially spaced from said end of said shaft and defining a cam surface, a first end of said element extending a certain distance from said axis of said shaft at predetermined positions of said shaft and bearing against said cam surface of said collar, said first end extending a lesser distance from said. axis of said shaft at positions intermediate said predetermined positions of said shaft, a second end of said element extending into said hole of said socket at said intermediate positions, thereby interlocking said wrench with said shaft.

3. In a tap changer mechanism, the combination of an operating shaft, a wrench defining a socket cooperative with one end of said shaft for rotating said shaft, and means for interlocking said wrench and said shaft, said means comprising a hole in the wall of the socket of said wrench and a detent cooperating with said end of said shaft and said socket, said detent including an element movable transversely of the axis of said shaft and rotatable with said shaft and a fixed collar coaxially spaced from said end of said shaft and defining a cam surface, movement of said element in contact with said cam surface of said collar causing said element to extend into said hole to interlock said wrench and said shaft when said shaft is rota-ted into a given position.

4. In a tap changer mechanism, the combination of an operating shaft, a wrench having a socket portion cooperative with one end of saidshaft for rotating said shaft, and means for interlocking said wrench and said shaft, said means comprising a hole in the socket portion of said wrench and a detent cooperating with said end of said shaft and said socket, said detent including an element movable transversely to the axis of said shaft rotatable with said shaft and a fixed collar coaxially spaced from said end of said shaft, said collar being divided into segments spaced circumferentially from one another defining a cam surface, said element bearing against one or more of said segments, rotation of said element with relation to said fixed collar causing said element to move transversely to said axis of said shaft, said element extending into the hole of said socket to interlock said wrench with said shaft when said element bears against only one of said segments.

5. A switch ope-rating mechanism including an operating shaft, said operating shaft comprising an operating nut defining driving surfaces for actuation by a wrench, said'operating nut having a retractable pin extending radially thereof, an operating wrench comprising a socket portion cooperative with said operating nut to rotate said shaft, said socket portion having an opening in the wall thereof, and a fixed collar surrounding said operating nut, a portion of said collar being divided into circumferentially spaced radially tapered segments defining a cam surface, one end of said pin extending from said nut toward said segments, said end of said pin extending a certain distance from the axis of said shaft when said end of said pin bears on adjacent two of said segments, said end extending a lesser distance from said axis of said shaft when said pin bears on only one of said segments, the other end of said pin extending from said nut into said opening when said one end of said pin bears on only one of said segments, said other end of said pin retracted into said nut when said one end of said pin bears on adjacent two of said segments, whereby said socket portion of said wrench is engageable with and disengageable from said nut when said one end of said pin bears on two of said segments and said wrench is incapable of being engaged with and disengaged from said nut when said one end of said pin bears on only one of said segments.

6. A switch operating mechanism including an operating shaft member having an end portion defining driving surfaces, an operating wrench member having a socket cooperative with said driving surfaces for rotating said shaft, a pin, a guide means in one of said members for holding said pin in a position transverse to the axis of said shaft, a spring means acting on said pin to force one end of said pin away from said axis of said shaft along said guide means, an opening in theother of said members, a fixed collar segment having a cam surface abutting said end of said pin and forcing said end of said pin along said guide means toward the axis of said shaft until at least the other end of said pin extends into said opening in response to rotation of said shaft into a given position, said spring means 7 forcing said other end of said pin out of said opening in response to "rotation of said shaft away from-said position.

11.. A switch operating mechanism including an operating .shaft member, said operating shaft comprising an operating nut defining driving surfaces for actuation by a wrench-an operating wrench member having a socket cooperative with said driving surfaces of said operating nut to rotate said shaft, and means for interlocking saidshaft and said wrench, said means including a pin, a spring, :a guide means in one of said members for said pin and said spring, an opening in the other of said members and a fixed collar coaxially spaced from said shaft, said spring acting between said guide means and said pin to tend to force one end of said pin out of said guide means, the inside surface of said collar having circumferentially spaced notches, said spring forcing said end of said pin against the inside surface of said collar, said end of said pin extending a certain distance from said guide means, and the other end of said pin extending within said opening whereby said wrench is interlocked with said shaft when said one end of said pin bears against the inside surface of said collar intermediate two adjacent said notches, said one end of-said pin extending a greater distance from said guide means when said one end extends into .one of said notches. I

.8. A switch operating mechanism including an operating .shaft member having an end portion defining driving surfaces for actuation by a wrench, a wrench member having a socket cooperative with said driving surfaces, and a means for interlocking said shaft and said wrench, one of said members having an opening therein, said means including anelement cooperable with said opening to interlock said shaft and said socket, a guide means in the other of said members for said element, a spring tending to force said element alongsaid guide means and out of cooperation with said opening, and a collar segmenthaving a cam surface in contact with said element for forcing said element into cooperation with said opening in response to movement of said shaft into a given position.

9. The combination of a shaft member, a fixed frame providing a support for said shaft mem her, an operating member cooperable with said shaft member for rotating said shaft member,

and means for interlocking said shaft member and said operating member at given positions of saidshaft member, said means comprising a cam fixed to said frame, a pin, guide means for supporting and guiding said pin, said guide means being mounted on one of said members, and a hole in the other of said members, said cam abutting one end of said'pin at said given positions of said shaft member for forcing said pin along said guide means to cause said pin to extend into said hole in said other member.

10. A switch operating mechanism including an operating-shaft, a wrench cooperative with said shaft for rotating said shaft through a plurality of predetermined positions, and means for interlocking said wrench and said shaft including an element movable to two positions relative to said shaft and means responsive to rotation of said shaft for causing said element to move from one to the other of said two positions, rotation of said shaft to a predetermined position moving said element to one of its two positions with a snap action and rotation of said shaft to a position different from any of said predetermined positions moving said element to the other of its two positions to interlock said wrench and said shaft and prevent separation of said wrench from said shaft.

11. A switch operating mechanism including an operating shaft, a wrench cooperative with said .shaft for rotating said shaft into predetermined positions, and a cam and a follower mounted for movement relative to each other in response to rotation of said shaft, said cam moving said follower into a position interlocking said shaft and said wrench when said shaft is intermediate said predetermined positions.

- FRANK E. GROMMES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 708,724 Merrick et a1 Sept. 9, 1902 1,018,080 Reston Feb. 20, 1912 1,334,489 Gormley Mar. 23, 1920 1,398,263 Hale Nov. 29, 1921 12,081,464 Stewart May 25, 1937 2,432,574 Josefiak Dec. 16, 1947 

